The present invention relates to a method of controlling the molybdenum content of a uranium product, i.e., yellowcake, and more particularly relates to controlling the molybdenum content of yellowcake (1) by controlling the pH of the eluate as the yellowcake precipitates from an eluate of ammonium carbonate and (2) by treating the precipitated yellowcake to remove substantial amounts of molybdenum that may coprecipitate with the uranium values.
In a uranium leach operation such as fully disclosed in U.S. application Ser. No. 732,234, filed Oct. 14, 1976, now abandoned, the uranium-bearing ore is contacted with an oxidant and a leach solution to dissolve the uranium values. The uranium values are then concentrated by passing the leach solution through an ion-exchange column or the like which adsorbs the uranium values from the leach solution. Next, an eluant, e.g., ammonium carbonate, is passed through the ionexchange column to desorb the uranium values in a greater concentration than existed in the leach solution. The pregnant eluate is then heated by steam stripping or the like to precipitate the uranium values, i.e., yellowcake, from the eluate.
In many areas where a leach operation, such as described above, is applicable, molybdenum values are also present in the ore. The molybdenum will react similarly to the uranium in that the molybdenum values will oxidize and will leach into the solution along with the uranium. Likewise, the molybdenum values will be adsorbed onto the ion-exchange column and are eluted from the resin along with the uranium values by the eluant. When the pregnant eluate is subjected to steam stripping, a portion of the molybdenum values, e.g., molybdic acid, will coprecipitate with the uranium values and is considered as an undesirable contaminant in the yellowcake. If the molybdenum content in the yellowcake exceeds a specified value, e.g., 0.6% by weight, the yellowcake may require further expensive processing before it will be accepted by a commercial refiner. Since molybdenum is not easily removed completely before the precipitation step, the need for reducing the amount of molybdenum coprecipitated with the yellowcake is readily apparent.